The present invention relates to a thermal analysis apparatus for measuring a signal representative of a change physical or chemical property of a sample as a function of temperature or time. More particularly, the invention relates to an thermal analysis apparatus which enables the atmospheric conditions surrounding a sample to be controlled throughout, before and after measurement, which has conventionally been difficult.
Thermal analysis is an effective means for examining as to how a material property is changed by time or temperature. The thermal analysis apparatuses generally known include, as typical examples, a differential scanning calorimeter (DSC), differential thermal analysis apparatus (DTA), thermogravimetric analysis apparatus (TG), thermomechanical analysis apparatus (TMA) and so on. These apparatuses have respective objects to measure sample enthalpy change, differential heat (qualitative enthalpy change), weight change and dimensional change as a function of temperature or time. In thermal analysis, a sample is varied in accordance with a programmed temperature function in order to measure simultaneously a signal from a converter for property value measurement and a temperature signal. The data of a combination of the property signal and temperature signal thus measured is usually represented on a temperature-property two dimensional coordinate. At this time, if a temperature program used differs, a different thermal analysis curve is generally obtained. Thus, the temperature program is one of the most important parameters representative of measuring conditions.
Also, heating up carbon in air produces an oxidizing decomposition reaction whereas a similar experiment if conducted in nitrogen does not cause a reaction. As may be inferred from this example, it is often the case that changing the atmosphere around a sample provides substantially different thermal analytic result. That is, in thermal analysis the atmosphere for a sample is also an important parameter to represent measurement conditions.
Most of the thermal analysis apparatuses presently marketed are structured such that a temperature program as mentioned above or measuring condition parameter such as atmosphere can be controllably set in order to secure reliability in measurement result.
Meanwhile, there is also an attempt to accommodate entirely a commercially available thermal analysis apparatus within a gas tight chamber for the purpose of desirably setting sample atmosphere throughout, before and after measurement.
In the commercially available thermal analysis apparatus, measurement can be made on sample atmosphere during measurement. However, it has been impossible or difficult to set for sample atmosphere upon placing a sample in the thermal analysis apparatus before measurement.
There are cases that a sample, as it may be, if merely allowed to stand in air at room temperature be subjected to oxidation or deliquescence. If thermal analysis is conducted on such a ample, a analytical result is changed by the atmosphere in an entire laboratory in addition to the atmosphere within the thermal analysis apparatus. Therefore it is clearly insufficient that sample atmosphere can be set only after placing a sample in the apparatus, from a viewpoint of securing reliability in measurement result.
On the other hand, the method of accommodating the entire apparatus in a gas tight chamber has an advantage in that it provides the capability of setting sample atmosphere before measurement. However, the chamber includes therein the heating oven so that heat is filled within the chamber and output signals of the apparatus are liable to become out of order. There are also problems in that the chamber is contaminated on the inside due to the discharge of a gas produced by sample decomposition, the gas if to be discharged from the sample chamber to a chamber outside makes piping complicate resulting in difficulty in keeping temperature of the piping system and hence incapability of analyzing the gas, and so on.